The Respiratory Death Airway Algorithm

Introduction

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Last week Scott Weingart discussed a case of a profoundly hypoxemic patient with a failed airway which was salvaged by surgical cricothyrotomy (listen to it here). Despite successfully resuscitating the patient there was some criticism later that perhaps a cricothyrotomy wasn't absolutely required. This reminds me of a case I've been planning to discuss here, a case looking at the same issue but from a different perspective.

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The Case

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Once upon a time at Genius General Hospital, there was an elderly man on the hospital ward who unexpectedly had a massive aspiration event, desaturated, became bradycardic, and went into cardiac arrest.A code was called and CPR was initiated.An anesthesiologist arrived and made multiple attempts at intubation before declaring “this is impossible, there is so much food here I can't see anything.”Efforts were made to find a scalpel or cricothyrotomy kit.Eventually a scalpel was located, and I initiated a surgical cricothyrotomy with a vertical incision.The incision was frighteningly bloodless and his cricoid membrane was easily palpable.Just as I was about to make the transverse incision, the anesthesiologist called out for me to stop, because he was finally able to intubate.Despite further rounds of CPR, the patient could not be resuscitated.

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Should we have proceeded to a surgical airway earlier?This patient clearly arrested due to respiratory failure and hypoxemia.He had an easily identifiable cricothyroid membrane.Cricothyrotomy likely would have taken 1-2 minutes, achieving definitive airway control much sooner.

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Background: Acceptable rates of error in medicine

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Medicine is an imperfect science, and some mistakes are inevitable.In certain areas, there are even specific accepted rates of failure!

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Perhaps the best known is the negative-appendectomy rate.This dates from before the advent of routine CT scans, when it was impossible to diagnose appendicitis with certainty.Although this may no longer apply today, the classic teaching was that a 15% negative-appendectomy rate was reasonable.A negative-appendectomy rate of zero would indicate that the surgeon was not being aggressive enough, whereas a negative-appendectomy rate >>15% would suggest that the surgeon was being too aggressive.

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A similar phenomenon applies to cardiac catheterization.It is impossible to determine in all cases whether a patient with chest pain and EKG changes may be having a transmural infarction.In some cases of uncertainty, if a significant suspicion exists for STEMI then it is appropriate to perform cardiac catheterization.It is universally accepted that in many of these cases (14% in one study), the catheterization will be negative.A cardiologist with a zero negative-catheterizationrate is too conservative selecting patients for catheterization.

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The error rate which I'm most familiar with is the failed-extubation rate.It is impossible to predict exactly which patients can be safely extubated.The only way to know for certain is to trial extubation.Although variable between studies, a reasonable extubation failure rate is probably in the neighborhood of 15% (Penuelas 2015).Having a failed-extubation rate of zero might sound good, but it would actually indicate insufficiently aggressive efforts to liberate the patient from mechanical ventilation.

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The benefit of an accepted failure rate

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Having an accepted failure rate is a powerful tool to defend physicians tasked with undertaking risky interventions.When a patient fails extubation and requires re-intubation, the entire ICU team feels bad about it.We re-think the case and wonder if there were any missed signs that the patient would fail.Perhaps we made a mistake, maybe we should have waited longer.Although reviewing poor outcomes is important, there is a risk that excessive guilt could cause us to be too passive in the future.It might cause us to leave the next patient on the ventilator days longer than necessary.

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Having an accepted extubation-failure rate is a critical tool to remind the ICU team that it's inevitable and acceptable to have an extubation failure.For every failed extubation, there are probably 6-12 patients who succeed, often pleasantly surprising us.It may be best to view reintubation as an unavoidable necessity rather than failure.

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What is an acceptable false-cric rate?

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A false-cric rate is impossible to measure in real life, but it is nonetheless an interesting concept.Let's imagine a patient with a failed airway despite multiple attempts at intubation and LMA, similar to the case that Scott Weingart discussed.The patient is spiraling rapidly down the vortex, and a surgical cricothyrotomy is appropriately performed.

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Now, let's imagine a parallel universe where surgical airway management doesn't exist.There is a high likelihood that without a surgical airway the patient would develop anoxic brain injury or death (indicating that cricothyrotomy was actually necessary, what might be called a “true-cric”).However, there is also some possibility that the patient would be OK.Perhaps the seventh intubation attempt would succeed.In this latter case the cricothyrotomy would not truly have been required (a “false-cric”).

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Unfortunately, it is impossible to ever actually know our false-cric rate.However, it is probably acceptable to have a fairly high false-cric rate (perhaps 25-50%?).Although cricothyrotomy is undesirable, it is vastly preferable to death or anoxic brain injury.Therefore, if there is a significant risk of anoxia, then it makes sense to proceed to cricothyrotomy.This principle is implicitly built into our airway algorithms, such as the vortex algorithm above.

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Perhaps Scott Weingart's cricothyrotomy was not 100% necessary (the only way to prove this with 100% certainty would be not to do the cricothyrotomy with a subsequent bad outcome).Maybe it was only 95% or 90% necessary.What if perhaps this was a “false-cric”?Well, in that case we should embrace it and accept it in the same way that we accept negative appendectomies, normal cardiac catheterizations, and failed extubations.The misconception that every cricothyrotomy is 100% necessary is dangerous, and runs contrary to basic airway management principles.

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The respiratory death airway algorithm

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Historically, the ACLS algorithm proceeded in the order A-B-C, with initial focus on securing the airway.In 2010 this was switched to C-A-B, with the initial focus on circulation (e.g., chest compressions and defibrillation).This makes sense for most patients.For the average cardiac arrest patient with VT/VF arrest, the focus should be on early defibrillation and high-quality chest compressions.For VT/VF, immediate establishment of a definitive airway is not the primary priority.

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However, there are a small fraction of cardiac arrests which are clearly due primarily to respiratory failure.Examples may include patients with progressive hypoxemic respiratory failure (e.g., due to pneumonia or aspiration) or patients with anatomic airway obstruction (e.g., angioedema or epiglottitis).For a patient with primary respiratory arrest, the priority should be placed on establishing an airway.The C-A-B approach may fail such patients.

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What is the appropriate approach to airway management for a patient with cardiac arrest due to respiratory failure?This will depend on the situation.In many cases proceeding directly to a definitive airway is a good approach (for example, a laryngeal mask airway will not address epiglottitis or angioedema).

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What algorithm should be used for definitive airway management here? The standard approach is often to attempt laryngoscopy. Although this often succeeds, the problem is that these patients have a very small time window in which an airway must be established to avert brain damage and death. They have already fallen entirely off the oxygen desaturation curve (figure above). If laryngoscopy fails, by the time a surgical airway is established it is probably too late.

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For this unique situation, it could make sense to proceed extremely aggressively to a definitive airway by simultaneously performing orotracheal intubation and cricothyrotomy. Although this may seem extreme, these patients are very likely to die without immediate airway management (indeed, in some sense they have already “died”). Proceeding in a stepwise manner through a typical airway algorithm may take too long.

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It may be acceptable to have a very high “false-cric” rate in this scenario.Logistically, these patients will have received at least one or two rounds of CPR before initiating cricothyrotomy. A patient with respiratory failure progressing to cardiac arrest refractory to initial resuscitative efforts has a grim prognosis, with any likelihood of a good outcome hinging on immediate reoxygenation.Trading a neck incision for more rapid airway control is a sensible trade-off, as even seconds can count in this situation.If the patient does survive, prognosis will typically depend primarily on the extent of brain injury.

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Never having actually done this, it remains a purely theoretical concept.I will be interested to see what other folks think about it.One limitation is that it is only applicable in cases where cardiac arrest is clearly due to primary respiratory failure.Especially for out-of-hospital arrests this may be impossible to discern, so usual algorithms should be used.

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Conclusion

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The technical difficulty of surgical cricothyrotomy with a finger-bougie techniqueis comparable to placing a surgical chest tube.This technique is relatively new, and we are only beginning to understand how it should fit into various airway algorithms in different situations.It likely remains underutilized.For example, in a patient with cardiac arrest due to loss of the airway, there is little benefit to delaying cricothyrotomy until after failure of laryngoscopy.

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I've always been trained that a clinician should not be faulted for intubating a patient if there was a genuine concern that the patient may lose their airway.It's easy to second-guess these decisions the next morning.However, unless you are at the bedside and are willing to accept responsibility of the decision not to intubate, then this is unfair.By the same token, a clinician should not be faulted for a surgical cricothyrotomy if there is immediate and genuine concern that the patient may otherwise die or suffer anoxic brain injury.

Josh, Excellent post. Funny, when I heard Scott's case I literally thought of the same EXACT analogy regarding historically appropriate false positive rates of surgeons for appendectomies. (In fact I almost included it in my comments on Scott's page) I couldn't agree more with your points. Along the theme of needing to be aggressive in deciding to cut the neck, I have thought a lot about about the scenario where it may be most prudent to try ZERO attempts from above and to proceed straight to Cricothyroidotomy. I will say though, that I have not thought about this mgghyhscenario in the pt who has suffered a cardiac arrest as a result of a primary respiratory arrest. It seems that these patients may not necessarily portend a difficult airway (w/regard to endotracheal intubation, or LMA placement) unless they have (as you mention) some sort of airway obstruction. Furthermore, the rate of oxygenation & ventilation in the arrested pt now becomes limited by low cardiac output. Overall, I think the cardiac arrest pt where we know for sure the pt suffered a respiratory arrest, and then further specifically know for certain it was as a result of obstruction would be rare. In… Read more »

Completely agree that there are some situations where a neck-first approach is safest. At Genius General we once received in transfer a tragic epiglottitis case identical to the scenario that you described. A neck-first approach would have been life-saving. Especially for a practitioner without a lot of experience with cricothyrotomy (i.e., most of us), this could allow a more controlled procedure with ongoing oxygenation. With ample intradermal lidocaine, this might not even require deep sedation. My guess is that the procedure isn't much more painful than a surgical chest tube.

Every situation is different. The algorithm above isn't meant to be followed rigidly. It is intended more as a conceptual construct: in the case of cardiac arrest due to respiratory failure there should probably be an extremely low threshold to rapidly and unapologetically cut to air, for any actual or predicted difficulty with intubation.